There are many methods for blocking crank calls in the prior art, for example, manual setting a blacklist by a user is a usual way for blocking the crank calls. The user can manually add a phone number from call history, a short message or a contact list or fill a phone number directly in the black list directly. The phone numbers listed in the blacklist are usually regarded as crank calls. The methods above relies on personal subjective judgment and the crank phone number is added manually, which has the advantage of adding the phone number correctly after testing and has the disadvantage of post processing, consuming personal energy, requiring manual adding, wasting time and energy and can not early block the crank calls which have not been received before.
In addition, a method for rejecting a wangiri call (a call that is cut off immediate after call ringing) exists in the prior art. The method adapts determining the time of ring tone of a call; if the time of the ring tone of the call is less than a certain threshold value and simultaneously accords with one or some of the following conditions, the phone number of the call is determined to be a crank phone number. For example, the conditions are as the following: the phone number of an incoming call is not in the phonebook of a cell phone; the phone number of the incoming call is not local; the number of the incoming call is not in the call record, and so on. Such method solves the problem that a user is disturbed by wangiri calls. However, for some promotional phone numbers and prank phone numbers, a receiver needs a long time analysis to determine whether a phone number is a crank phone number or not, which wastes a great deal of time and energy.
At present, blacklists of part cell phone anti-crank products are collected via Internet and correctness of phone number data needs to be examined. It can not determine whether a phone number is being reported maliciously. If the correctness of the phone number can not be verified, the interest of a person who is accused falsely or reported by mistake will be damaged.
In addition, at present, the data of blacklists of parts of cell phone anti-crank products is relatively large. Currently, millions of crank phone numbers are reported in China. It is estimated that more than ten millions of phone numbers would be reported as crank phone numbers in the near future. Researching a database of the crank phone number above requires some time and it is impossible to complete crank phone number investigation in 1 or 2 seconds after receiving a call or a short message. Therefore, it is necessary to improve researching of the blacklist at the client/cell phone or shorten the blacklist.